JP5272342B2 - Thin film transistor substrate manufacturing method and image display device - Google Patents

Description

The present invention relates to a method for manufacturing a flexible thin film transistor substrate and an image display device using the thin film transistor substrate manufactured thereby.

The flexible display is light and easy to carry, and unlike the glass substrate, it has the advantage that it does not break, so the market is expected to grow significantly in the near future.
However, the biggest problem in realizing a flexible display is how to realize a flexible back plate (TFT array). Conventionally used amorphous silicon TFTs have a problem that their film forming temperature is as high as 250 ° C. or higher, and thus are difficult to apply to plastic substrates. In addition, organic TFTs, which are expected to dominate future TFTs from the viewpoint that they can be produced by printing methods, are thought to require more time for full-scale practical use due to their long-term stability and low characteristics. It is done. Under such circumstances, a transparent amorphous oxide semiconductor that can be produced at room temperature and has high performance has been reported in recent years (see Non-Patent Document 1).
K. Nomura et.al., Nature 432, 488 (2004)

  However, when a TFT is formed on a polymer substrate, the adhesion between the polymer substrate and the thin film used for the TFT is inferior to that of the glass substrate, so the thin film is easily peeled off due to residual stress, etc. There is a problem that can not be.

  The present invention has been made in view of the above points, and a thin film transistor substrate capable of removing a thin film transistor formed on a flexible substrate and obtaining a product having excellent reliability and durability, and a thin film transistor substrate including the thin film transistor substrate. An object is to provide an image display device used.

To achieve the above object, the invention of claim 1 includes a flexible substrate, a first underlayer, a second underlayer, a gate electrode, an auxiliary capacitor electrode, a gate insulating layer, a source electrode, and a drain. A method of manufacturing a thin film transistor substrate comprising an electrode, a semiconductor active layer made of a metal oxide, and a thin film transistor circuit having a pixel electrode, wherein an organic material, an inorganic material is formed on a surface which is a first surface of the flexible substrate The first base layer made of any of the organic-inorganic hybrid materials is formed by any one of a wet coating method, a vapor deposition method, and a CVD method, and on the back surface, which is the second surface of the flexible substrate, organic materials, inorganic materials, wet coating method the second underlayer made of either an organic-inorganic hybrid material, an evaporation method, a thick film thickness than the thickness of the first undercoat layer by any of the methods CVD method Forming a conductive thin film made of a metal material or a transparent conductive oxide material on the first underlayer, and patterning the conductive thin film into a desired shape to form the gate electrode and the auxiliary capacitor electrode. Forming the gate insulating film on the upper surface of the first base layer excluding the upper surface of the gate electrode and the auxiliary capacitor electrode and the upper surface, forming an amorphous thin film on the gate insulating film, and forming the amorphous thin film To form a semiconductor active layer facing the gate electrode by forming a conductive thin film made of a metal material or a transparent conductive oxide material on the gate insulating film and the semiconductor active layer, The conductive thin film is patterned into a desired shape to form the source electrode and the drain electrode that are conducted to the semiconductor active layer. An interlayer insulating film is formed on the upper surface of the source electrode and the drain electrode and the upper surface of the gate insulating film excluding the upper surface, and a through-hole leading to the drain electrode is formed in the interlayer insulating film by photolithography, and the interlayer insulating film The thin film transistor circuit is configured by forming the pixel electrode that is electrically connected to the drain electrode through the through hole on the upper surface of the thin film transistor.

The invention of claim 2 is the method for producing a TFT substrate of claim 1, wherein the thickness of the first undercoat layer is 2nm or more 7μm or less.

It the invention of claim 3, in the manufacturing method of a thin film transistor substrate according to claim 1 or 2, wherein at least one of said first base layer and the second base layer, an ultraviolet curable resin or a thermosetting resin It is characterized by.
The invention of claim 4 is the method of manufacturing a thin film transistor substrate according to claim 1 or 2 , wherein at least one of the first underlayer and the second underlayer made of the inorganic material is an oxide, a nitride, It is one of oxynitrides.

According to a fifth aspect of the present invention, in the method of manufacturing a thin film transistor substrate according to the third aspect , the ultraviolet curable resin or the thermosetting resin is any one of an acrylic resin, an organosilicon resin, and a polysiloxane resin. To do.
The invention of claim 6 is the method for manufacturing a thin film transistor substrate according to claim 4 , wherein the oxide or nitride or oxynitride is silicon oxide, silicon oxynitride, silicon nitride, alumina, titanium oxide, niobium oxide, or oxide. It is one of gallium.

A seventh aspect of the present invention is an image display device, the thin film transistor substrate manufactured by the method of manufacturing a thin film transistor substrate according to any one of the first to sixth aspects, and an image display provided on the thin film transistor substrate. And a medium.
According to an eighth aspect of the present invention, in the image display device according to the seventh aspect , the image display medium is a liquid crystal.
According to a ninth aspect of the present invention, in the image display device according to the seventh aspect , the image display medium is an electrophoretic type.

According to the thin film transistor substrate manufacturing method and the image display device using the thin film transistor substrate manufactured by the manufacturing method according to the present invention , the first lower surface provided on one surface of the flexible base material on which the thin film transistor is formed is provided. The thickness of the base layer is made thinner than the thickness of the second base layer provided on the other surface of the flexible base material on which the thin film transistor is not formed, and the semiconductor activity made of oxide on the first base layer A semiconductor circuit comprising a layer, a gate electrode, a source electrode, a drain electrode, a thin film transistor comprising a gate insulating film disposed between the gate electrode and the semiconductor active layer, and a wiring constituted by a conductive material having an electrical contact with the transistor is formed. As described above, a flexible thin film transistor substrate that does not easily peel off and has excellent durability and reliability, and a method using the same Image display device can be realized.

  In addition, according to the present invention, a flexible thin film transistor substrate that is less prone to film peeling and excellent in productivity by controlling the film thickness of the first underlayer in the range of 2 nm to 7 μm and the same are used. An image display device can be provided.

(First embodiment)
Embodiments of a thin film transistor substrate manufacturing method and an image display device using the thin film transistor substrate manufactured by the manufacturing method according to the present invention will be described below in detail with reference to the drawings.

The flexible substrate 1 used in the present invention is only required to be flexible. Specifically, polymethyl methacrylate, polyacrylate, polycarbonate, polystyrene, polyethylene sulfide, polyethersulfone, polyolefin, polyethylene terephthalate, polyethylene naphthalate. , Cycloolefin polymer, polyethersulfene, triacetyl cellulose, polyvinyl fluoride film, ethylene-tetrafluoroethylene copolymer resin, weather resistant polyethylene terephthalate, weather resistant polypropylene, glass fiber reinforced acrylic resin film, glass fiber reinforced polycarbonate, polyimide Fluorine resin, cyclic polyolefin resin, liquid crystal polymer and the like can be used. However, the flexible base material 1 concerning this invention is not limited to these.
In addition, the materials constituting these flexible base materials contain known additives such as antistatic agents, ultraviolet absorbers, plasticizers, lubricants, colorants, antioxidants, flame retardants, etc. Can also be used. These may be used as a single substrate, but a composite substrate in which two or more kinds are laminated can also be used.

For the first and second base layers 2 and 3 used in the present invention, an organic material, an inorganic material, an organic-inorganic hybrid material, or the like can be used. Further, part of the first and second underlayers may be conductive, but at least the outermost surface on which the semiconductor circuit is formed needs to be insulative.
The organic material is not particularly limited as long as it has appropriate hardness and mechanical strength. However, materials that can use curable resins or thermosetting resins by irradiation with ionizing radiation or ultraviolet rays are preferable, and examples include ultraviolet irradiation curable acrylic resins, organosilicon resins, and thermosetting polysiloxane resins. It is not limited to. These materials are produced by known methods such as wet coating (dip coating, spin coating, flow coating, spray coating, roll coating, gravure coating, etc.), vapor deposition, and CVD (Chemical Vapor Deposition). Although formed, the wet coating method is particularly preferable from the viewpoint of ease of processing into a large area and cost.

In addition, as the inorganic material, materials such as oxide, nitride, oxynitride and the like are particularly preferable. However, it is not limited to these. Specific examples include silicon oxide, silicon oxynitride, silicon nitride, alumina, titanium oxide, niobium oxide, and gallium oxide, but are not limited thereto. In addition, these materials do not necessarily have a composition in accordance with the stoichiometric ratio, and it is also preferable to take a composition that deviates from the stoichiometric ratio in consideration of adhesion and stress value. These materials are sol-gel wet coating, vapor deposition (reactive vapor deposition, plasma assisted vapor deposition), sputtering (RF magnetron sputtering, DC magnetron sputtering, reactive sputtering), CVD (plasma). It is formed by a known method such as a CVD method, a thermal CVD method, a photo CVD method, a How-wire CVD method) or laser ablation. As the organic-inorganic hybrid material, a known material such as a material in which silica particles or titania particles are embedded in an organic material is used.
The first and second underlayers can be processed in a single-wafer type or can be wound and produced, but are preferably wound and produced from the viewpoint that they can be supplied at low cost and in large quantities.
Further, the first and second underlayers need to be formed on both surfaces of the flexible base material. By doing so, it is possible to prevent degassing from the flexible base material and realize a highly reliable semiconductor circuit, and at the same time, keep the mechanical strength of the flexible base material high.

The film thickness of the first base layer 2 formed on the surface of the flexible substrate 1 on the side where the semiconductor circuit 4 is formed is the back surface of the flexible substrate 1 on the side where the semiconductor circuit 4 is not formed. It is made thinner than the film thickness of the 2nd foundation | substrate layer 3 formed in this. By doing so, it is possible to prevent peeling of the semiconductor circuit due to film stress and to prevent curling due to the presence of the thick second base layer 3.
Further, by controlling the film thickness of the first base layer 2 to be 2 nm or more and 7 μm or less, a thin film transistor substrate with high reliability and low cost can be provided. If the film thickness is thinner than 2 nm, it is difficult to stably form the first underlayer 2 over a wide area. On the other hand, if the film thickness is larger than 7 μm, the film is cracked or curled by stress or the like.

As shown in FIG. 2, the semiconductor circuit 4 shown in the present embodiment includes a gate electrode 6, an auxiliary capacitor electrode 7, a gate insulating film 8, a source electrode 9, a drain electrode 10, a semiconductor active layer 11, an interlayer insulating film 12, The pixel electrode 13 is provided.
The semiconductor circuit 4 includes a wiring (not shown) made of a conductive material for connecting the various electrodes to electrical contacts (not shown).

In addition, the gate electrode 6, the source electrode 9, the drain electrode 10, the auxiliary capacitor electrode 7, the pixel electrode 13, the scanning line electrode, and the signal line electrode used in the semiconductor circuit 4 include Al, Ta, Cr, Mo, Au, Ag, Metal materials such as Cu, indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), cadmium oxide (CdO), indium cadmium oxide (CdIn ₂ O ₄ ), cadmium tin oxide (Cd ₂ Transparent conductive oxide materials such as SnO ₄ ), zinc tin oxide (Zn ₂ SnO ₄ ), and indium zinc oxide (In—Zn—O) are preferably used. However, it is not limited to these. Moreover, what doped this impurity to the oxide material is also used suitably. For example, indium oxide doped with tin (Sn), molybdenum (Mo), titanium (Ti), tin oxide doped with antimony (Sb) or fluorine (F), zinc oxide with indium, aluminum, gallium ( For example, doped with Ga). Among these, indium tin oxide (commonly known as ITO) in which tin (Sn) is doped into indium oxide is particularly preferably used because of high transparency and low resistivity.

  In addition, a laminate in which a plurality of thin films of the conductive oxide material and a metal such as Au, Ag, Cu, Cr, Al, Mg, Li, and Ta are stacked can be used. In this case, a three-layer structure in which a conductive oxide thin film / metal thin film / conductive oxide thin film is laminated in order in order to prevent oxidation or deterioration with time of the metal material is particularly preferably used. The gate electrode, the source electrode, the drain electrode, the auxiliary capacitor electrode, the pixel electrode, the scanning line electrode, and the signal line electrode may be the same material, or may be all different materials. However, in order to reduce the number of steps, it is more desirable that the gate electrode and the auxiliary capacitor electrode, the source electrode and the drain electrode are made of the same material. These electrodes can be formed by a vacuum deposition method, an ion plating method, a sputtering method, a laser ablation method, a plasma CVD method, a photo CVD method, a hot wire CVD method, screen printing, letterpress printing, an ink jet method or the like. However, it is not limited to these methods.

The semiconductor active layer made of an oxide used in the image display device of the present invention is an oxide containing one or more elements of zinc, indium, tin, tungsten, magnesium, gallium, and titanium. For example, known materials such as zinc oxide, indium oxide, indium zinc oxide, tin oxide, tungsten oxide (WO), and zinc gallium indium oxide (In-Ga-Zn-O) can be used. However, it is not limited to these. Since the semiconductor active layer made of an oxide can be formed at a low temperature, it is particularly suitably used when forming a semiconductor circuit on a flexible substrate. The structure of these materials may be single crystal, polycrystal, microcrystal, crystal / amorphous mixed crystal, nanocrystal scattered amorphous, or amorphous. The electron carrier concentration of the oxide semiconductor material is preferably 10 ¹⁸ / cm ³ or less.
The oxide semiconductor layer is formed by a sputtering method, a pulse laser deposition method, a vacuum deposition method, a CVD method, an MBE (Molecular Beam Epitaxial) method, a sol-gel method, or the like, but preferably a sputtering method or a pulse laser deposition method. The vacuum evaporation method and the CVD method. Examples of sputtering include RF magnetron sputtering, DC sputtering, vacuum deposition includes heating deposition, electron beam deposition, ion plating, and CVD includes hot wire CVD and plasma CVD. Absent.

The material used for the gate insulating film of the thin film transistor used in the present invention is not particularly limited, but silicon oxide, silicon nitride, silicon oxynitride (SiNxOy), aluminum oxide, tantalum oxide, yttrium oxide, hafnium oxide, hafnium aluminate, Inorganic materials such as zirconia oxide and titanium oxide, or polyacrylates such as PMMA (polymethyl methacrylate), PVA (polyvinyl alcohol), PS (polystyrene), transparent polyimide, polyester, epoxy, polyvinylphenol, polyvinyl alcohol, etc. However, it is not limited to these. In order to suppress the gate leakage current, the resistivity of the insulating material is 10 ¹¹ Ωcm or more, preferably 10 ¹⁴ Ωcm or more.
The insulating layer is formed using a method such as vacuum deposition, ion plating, sputtering, laser ablation, plasma CVD, photo CVD, hot wire CVD, spin coating, dip coating, or screen printing. . The thickness of the insulating layer is desirably 50 nm to 2 μm. These gate insulating films may be used as a single layer, may be a laminate of a plurality of layers, or may have a composition inclined in the growth direction.

The configuration of the thin film transistor (semiconductor circuit) used in the present invention is not particularly limited. Either a bottom contact type or a top contact type may be used, and either a top contact type or a bottom contact type may be used. In addition, it is preferable to increase the aperture ratio by providing an interlayer insulating film over the thin film transistor used in the present invention and further providing a pixel electrode electrically connected to the drain electrode thereon.
The interlayer insulating film is not particularly limited as long as it is insulative and substantially transparent. For example, silicon oxide, silicon nitride, silicon oxynitride (SiNxOy), aluminum oxide, tantalum oxide, yttrium oxide, hafnium oxide, hafnium aluminate, zirconia oxide, titanium oxide and other inorganic materials, or PMMA (polymethyl methacrylate) Examples thereof include, but are not limited to, polyacrylates such as PVA (polyvinyl alcohol), PS (polystyrene), transparent polyimide, polyester, epoxy, polyvinylphenol, and polyvinyl alcohol. The interlayer insulating film may be the same material as the gate insulating film or may be a different material. These interlayer insulating films may be used as a single layer, or a laminate of a plurality of layers may be used.

  In the case of an element having a bottom gate structure, it is also preferable to provide a protective film that covers the semiconductor layer. By using the protective film, it is possible to prevent the semiconductor layer from being changed with time due to humidity or the like or affected by the interlayer insulating film. As protective film, inorganic materials such as silicon oxide, silicon nitride, silicon oxynitride (SiNxOy), aluminum oxide, tantalum oxide, yttrium oxide, hafnium oxide, hafnium aluminate, zirconia oxide, titanium oxide, or PMMA (polymethyl methacrylate) ), And the like, but are not limited to these. PVA (polyvinyl alcohol), PS (polystyrene), transparent polyimide, polyester, epoxy, polyvinylphenol, polyvinyl alcohol, fluorine resin, and the like. These protective films may be used as a single layer or may be a laminate of a plurality of layers.

  The pixel electrode must be electrically connected to the drain electrode of the thin film transistor. Specifically, the interlayer insulation film is patterned by screen printing or the like, and the interlayer insulation film is not provided on the drain electrode, or the interlayer insulation film is applied over the entire surface and then correlated with laser beams, etc. For example, a method of making a hole in the film.

As the image display element 5 in the present invention, a liquid crystal display device in which liquid crystal is encapsulated, an electrophoretic display device filled with a dispersion medium solution and charged electrophoretic particles, and a surface having a charge dispersed in the dispersion medium solution Rotating particle display device filled with rotating particles having a region, electro-powder fluid system display that moves a pulverulent fluid enclosing a pulverulent fluid that exhibits high fluidity in an aerosol state in which a solid substance is stably suspended as a dispersoid in a gas Examples thereof include a liquid crystal display device and an electrophoretic display device. These image display elements are required to be flexible.
An embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

Next, examples of the present invention will be described.
As the substrate 1 for forming a semiconductor circuit, PEN (polyethylene naphthalate) 125 mm [Q65FA manufactured by Teijin DuPont Co., Ltd.] was used, and first and second underlayers as shown in Table 1 were formed.

In Table 1, the SiO2 film for forming the first and second underlayers was formed by the plasma CVD method. TEOS (tetraethoxyorthosilicate) and oxygen gas were used as raw materials. TEOS was warmed at 80 ° C. and O ₂ gas [flow rate 5 SCCM] was introduced as a carrier gas. The operating pressure was 0.002 Torr, the input power was 500 W, and the PEN film was warmed at 50 ° C. during film formation. The film thickness was changed by adjusting the film formation time.
The acrylic resin was formed on the PEN film by a bar coating method and cured with ultraviolet rays. The film thickness was changed by the number of lines of the bar coater.

On the various flexible base films thus prepared, Al was formed in a thickness of 50 nm by resistance heating vapor deposition. The Al thin film was patterned into a desired shape to form a gate electrode 6 and an auxiliary capacitor electrode 7. Further, a SiON thin film having a thickness of 330 nm was formed thereon by RF sputtering using a silicon nitride (Si ₃ N ₄ ) target to form a gate insulating film 8. Furthermore, as the semiconductor active layer 11, an amorphous In—Ga—Zn—O thin film was formed to 35 nm by RF sputtering using an InGaZnO ₄ target and patterned into a desired shape. On top of that, a resist was applied, dried and developed, and then Al was formed to 70 nm by resistance heating vapor deposition, and lift-off was performed to form the source electrode 9 and the drain electrode 10. Further, an epoxy resin was applied by a spin coating method with a thickness of 3 μm, and a through hole was formed on the drain electrode by a photolithography method to form an interlayer insulating film 12. Finally, Al was deposited to a thickness of 100 nm by resistance heating vapor deposition and patterned to form a pixel electrode 13. Table 2 shows the conditions for forming each film.
All film formation was performed at room temperature. The number of thin film transistor pixels of the semiconductor circuit manufactured here is 80 × 60, and the pixel size is 250 μm × 250 μm. The electrophoretic image display element 5 was pasted on the flexible semiconductor circuit thus prepared to produce an electrophoretic image display device.

  Table 3 summarizes the presence or absence of film peeling of the formed flexible semiconductor circuit, the warp of the element, and the driving state of the electrophoretic image display device thus manufactured.

  As is clear from the above results, if the thickness of the first underlayer 2 is thinner than that of the second underlayer 3 and the thickness of the first underlayer 2 is 2 nm or more and 7 μm or less, the reliability is improved. An excellent flexible image display device can be realized.

It is a schematic sectional drawing of the image display apparatus in embodiment of this invention. FIG. 3 is a partial cross-sectional view corresponding to approximately one pixel of the image display device of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Flexible base material, 2 ... 1st base layer, 3 ... 2nd base layer, 4 ... Semiconductor circuit, 5 ... Image display element, 6 ... Gate electrode, 7 ... Auxiliary Capacitor electrode, 8... Gate insulating film, 9... Source electrode, 10... Drain electrode, 11... Semiconductor active layer, 12.

Claims (9)

A flexible substrate, a first base layer, a second base layer, a gate electrode, an auxiliary capacitor electrode, a gate insulating layer, a source electrode, a drain electrode, a semiconductor active layer made of a metal oxide, and a pixel electrode A method of manufacturing a thin film transistor substrate comprising a thin film transistor circuit comprising:
The first base layer made of any one of an organic material, an inorganic material, and an organic-inorganic hybrid material is applied to the surface that is the first surface of the flexible base material by any of a wet coating method, a vapor deposition method, and a CVD method. Formed by the method
The second base layer made of any one of an organic material, an inorganic material, and an organic-inorganic hybrid material is applied to the back surface, which is the second surface of the flexible base material, by any one of a wet coating method, a vapor deposition method, and a CVD method. forming a thick film thickness than the thickness of the first undercoat layer by a method,
Forming a conductive thin film made of a metal material or a transparent conductive oxide material on the first underlayer;
Patterning the conductive thin film into a desired shape to form the gate electrode and the auxiliary capacitor electrode;
Forming the gate insulating film on the upper surface of the first base layer excluding the upper surface of the gate electrode and the auxiliary capacitor electrode and the upper surface;
Forming an amorphous thin film on the gate insulating film;
Patterning the amorphous thin film into a desired shape to form a semiconductor active layer facing the gate electrode;
Forming a conductive thin film made of a metal material or a transparent conductive oxide material on the gate insulating film and the semiconductor active layer;
Patterning the conductive thin film into a desired shape to form the source electrode and the drain electrode connected to the semiconductor active layer;
Forming an interlayer insulating film on the upper surface of the gate insulating film excluding the upper surface of the source electrode and the drain electrode and the upper surface;
Opening a through-hole leading to the drain electrode by photolithography in the interlayer insulating film,
Forming the pixel electrode conducting to the drain electrode through the through hole on the upper surface of the interlayer insulating film to constitute the thin film transistor circuit;
A method for manufacturing a thin film transistor substrate, comprising: Method for producing a TFT substrate of claim 1, wherein a thickness of the first undercoat layer is 2nm or more 7μm or less. The first at least one of the underlayer and the second underlayer, method according to claim 1 or 2, wherein the thin film transistor substrate is characterized in that an ultraviolet curable resin or a thermosetting resin. 3. The thin film transistor according to claim 1, wherein at least one of the first base layer and the second base layer made of the inorganic material is any one of oxide, nitride, and oxynitride. A method for manufacturing a substrate. 4. The method of manufacturing a thin film transistor substrate according to claim 3, wherein the ultraviolet curable resin or the thermosetting resin is any one of an acrylic resin, an organosilicon resin, and a polysiloxane resin. 5. The thin film transistor substrate according to claim 4, wherein the oxide, nitride, or oxynitride is any one of silicon oxide, silicon oxynitride, silicon nitride, alumina, titanium oxide, niobium oxide, and gallium oxide. Production method. The image display apparatus characterized by comprising: a thin film transistor substrate produced by the TFT substrate manufacturing method according, to the image display medium provided on the TFT substrate in any one of claims 1 to 6. 8. The image display device according to claim 7, wherein the image display medium is a liquid crystal. The image display device according to claim 7 , wherein the image display medium is of an electrophoretic method.

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